KR102390910B1 - Method and apparatus for calibration of light scattering sensor for measuring fine dust concentration - Google Patents

Abstract

An air particle meter can irradiate light to standard particles generated from a particle generator. The air particle meter may detect the number of particles per size of particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light. The air particle meter may determine a central channel based on the number of particles per size of particles. The air particle meter may calibrate an optical sensor so that the central channel has a preset channel value. By calibrating the optical sensor, it is possible to reduce a deviation between apparatuses.

Description

Calibration method and device of optical sensor for measuring fine dust concentration

Embodiments of the present invention relate to an airborne particle meter and an operating method thereof.

Particles floating in the atmosphere for a long period of time are fine dust with a particle size of less than 10 PM, called fine dust. The unit of PM (Particulate Matter)10 is a unit that refers to fine dust less than 10um. That is, fine dust less than 10 micrometers is called fine dust. Ultrafine dust refers to dust with a size of PM2.5 (less than 2.5um) as ultrafine dust.

One of the fine dust measurement methods is to detect the light reflected by the fine dust by emitting a light source (laser light, infrared) into the atmosphere. Scattered light generates an electrical signal, and information on the size and number of fine dust can be obtained through the frequency, length, and intensity of the electrical signal.

The above method is a method of measuring fine dust through an optical sensor, and the other method is very expensive. The method of measuring fine dust through an optical sensor may require a self-calibration function for sensor data reliability as the sensor cleaning cycle is too short due to contamination when used for a long time. Even if it points to other values, the reliability is much lower than that of expensive equipment.

Embodiments of the present invention, it is possible to provide an airborne particle meter and an operating method thereof. In order to reduce the deviation between the fine dust concentration measuring equipment, it is possible to perform calibration by applying the central channel.

Technical problems to be achieved in the embodiments are not limited to the matters mentioned above, and other technical problems not mentioned may be considered by those of ordinary skill in the art from various embodiments to be described below. can

A calibration method of an optical sensor (light scattering sensor) performed in at least one airborne particle measuring device, the method comprising: irradiating light to standard particles generated from a particle generator; detecting the number of particles per size of particles included in the standard particles based on the number of scattered light and the amount of scattered light by the standard particles; determining a central channel based on the number of each size of the particles; and calibrating the optical sensor so that the central channel has a preset channel value.

Here, the size of the particles may be classified into 254 channels.

Here, the central channel may be determined based on a first channel having the largest number of particles among candidate channels having a size difference between the preset channel and a preset first threshold value.

Here, calibrating the optical sensor so that the central channel has a preset channel value may include: calculating a difference value between the preset channel and the central channel; and moving the particle size detected by the optical sensor by the difference value.

Here, the preset channel may be determined based on the size of the standard particle.

One embodiment of the present invention in the air particle meter, a processor (processor); optical sensor; and memory; comprising: irradiating light to standard particles generated from the particle generator; detecting the number by size of particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light; determining a central channel based on the number of each size of the particles; And it may be set to calibrate the optical sensor so that the central channel has a preset channel value.

Here, the size of the particles may be classified into 254 channels.

Here, the central channel may be determined based on a first channel having the largest number of particles among candidate channels having a size difference between the preset channel and a preset first threshold value.

Here, the processor calculates a difference value between the preset channel and the center channel; And it may be further set to move the particle size detected by the optical sensor by the difference value.

Here, the preset channel may be determined based on the size of the standard particle.

According to embodiments, a concept of a central channel may be defined, and optical sensors may be calibrated based on the central channel. If the optical sensors are calibrated with respect to the center channel, better calibration results can be obtained than calibration using the existing channel mass value. Calibration using the center channel can achieve better calibration results that can dramatically reduce the deviation between instruments.

Effects obtainable from the embodiments are not limited to the effects mentioned above, and other effects not mentioned are clearly derived and understood by those of ordinary skill in the art based on the following detailed description. can be

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description to aid understanding of the embodiments, provide various embodiments and, together with the detailed description, explain technical features of the various embodiments.
1 is a diagram illustrating an optical sensor according to an embodiment of the present invention.
2 is a block diagram showing the configuration of a particle measuring device in the air according to an embodiment of the present invention.
3 is a diagram illustrating an embodiment of a method of operating a particle meter in the air.
4 is a diagram illustrating an embodiment in which an optical sensor detects particles.
5 is a view showing measurement results of optical sensors measuring the same standard particle.
6 is a diagram illustrating an example of a calibration result using a channel mass value.
7 is a diagram illustrating an embodiment of a standard particle center channel.
8 is a diagram illustrating an example of equipment performing center channel calibration and results of not performing center channel calibration.
9 is a diagram illustrating an embodiment of a result of performing center channel calibration.

The following embodiments combine elements and features of the embodiments in a predetermined form. Each component or feature may be considered optional unless explicitly stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, various embodiments may be configured by combining some components and/or features. The order of operations described in various embodiments may be changed. Some features or features of one embodiment may be included in another embodiment, or may be replaced with corresponding features or features of another embodiment.

In the description of the drawings, procedures or steps that may obscure the gist of various embodiments are not described, and procedures or steps that can be understood at the level of those of ordinary skill in the art are also not described. did

Throughout the specification, when a part is said to "comprising or including" a certain component, it does not exclude other components unless otherwise stated, meaning that other components may be further included. do. In addition, terms such as "...unit", "...group", and "module" described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. can be implemented as Also, "a or an," "one," "the," and like related terms are used herein in the context of describing various embodiments (especially in the context of the claims that follow). Unless indicated otherwise or clearly contradicted by context, it may be used in a sense including both the singular and the plural.

Hereinafter, embodiments according to various embodiments will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION The detailed description set forth below in conjunction with the appended drawings is intended to describe exemplary embodiments of various embodiments, and is not intended to represent the only embodiments.

In addition, specific terms used in the various embodiments are provided to help the understanding of the various embodiments, and the use of these specific terms may be changed to other forms without departing from the technical spirit of the various embodiments. .

1, an optical sensor (light scattering sensor) according to an embodiment of the present invention generates light scattered by dust in the air, but includes a laser having a lens for focusing, and the laser It may be composed of a body having a built-in detector that senses the size and number of suspended particles through the size and number of light generated while colliding with and scattering dust floating in the air. The optical sensor includes a plate-shaped body having a predetermined thickness, a cover for covering one side of the body, a cover for covering the other side of the body, and a body installed on one side of the body. and an air intake for sucking air into the interior. A dust measuring space communicating with the air intake, a laser installed on one side of the dust measuring space, a detector attached to an inner surface of the dust measuring space, communicating with the dust measuring space and facing the laser It may include a light extinction unit positioned so as to be possible.

The optical sensor may irradiate light to the particles and detect the size of the particles based on a voltage level according to the amount of scattered light scattered from the particles.

The dust measuring space is a space for measuring dust contained in the introduced external air, and the laser light passing through the lens collides with the dust particles floating in the dust measuring space and is scattered. to be sensed. The detector serves to detect the size and number of suspended particles through the size and number of light generated when the laser meets dust particles and scatters light. At this time, one or more detectors are installed on the inner surface of the dust measuring space for sensing the scattered light within the dust measuring space, but are configured to be as close to the laser as possible within the range that does not interfere with the laser. need. This is because, due to the characteristics of the straight-line laser beam, most light is reflected in the direction opposite to the direction of light travel, so it is the position where the measurement can be performed most accurately.

The optical sensor calibration method is inserted into a computing device such as a PC in a state recorded on a recording medium such as a CD (Compact Disc) or USB (Universal Serial Bus) memory and is performed through an access operation of the computing device or from the recording medium. After being stored in the storage space of the computing device, it may be performed through an access operation of the computing device.

Meanwhile, when the computing device or the portable terminal can access a server connected to the Internet, the optical sensor calibration method may be performed on the optical sensor according to a request from the computing device or the portable terminal.

Hereinafter, a computing device, a portable terminal, or a server on which the optical sensor calibration method is executed may be collectively referred to as a fine dust concentration measuring device.

The air particle measuring device may have the same configuration as the fine dust concentration measuring device illustrated in FIG. 2 , and the fine dust concentration measuring device may not be limited to the fine dust concentration measuring device shown in FIG. 1 .

2 is a block diagram showing the configuration of a particle measuring device in the air according to an embodiment of the present invention.

Referring to FIG. 2 , the air particle measuring device 200 may include a communication unit 210 , a processor 220 , and a DB 230 . In the server 200 of FIG. 2, only the components related to the embodiment are shown. Accordingly, it can be understood by those skilled in the art that other general-purpose components may be further included in addition to the components shown in FIG. 2 .

The communication unit 210 may include one or more components that enable wired/wireless communication between terminals. For example, the communication unit 210 may include at least one of a short-range communication unit (not shown) and a mobile communication unit (not shown). In the airborne particle meter 200, the communication unit 210 may not be an essential element, and may be omitted.

For example, a request generated according to a program code stored in a recording device such as the DB 230 may be transmitted to the terminal through a network under the control of the communication unit 210 . Conversely, a control signal, command, content, file, etc. provided under the control of the processor of the terminal may be received by the server 200 through the communication unit 210 through the network. For example, a control signal, command, content, file, etc. of the server 200 received through the communication unit 210 may be transmitted to the processor 220 or transmitted to the DB 230 and stored.

The DB 230 is hardware for storing various data processed in the server 200 , and may store a program for processing and controlling the processor 220 .

DB 230 is a random access memory (RAM), such as dynamic random access memory (DRAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), CD- It may include ROM, Blu-ray or other optical disk storage, a hard disk drive (HDD), a solid state drive (SSD), or flash memory. The DB 230 may be referred to as a memory.

The processor 220 controls the overall operation of the server 200 . For example, the processor 220 may generally control the input unit (not shown), the display (not shown), the communication unit 210 , the DB 230 , and the like by executing programs stored in the DB 230 . The processor 220 may control the operation of the external server 200 by executing programs stored in the DB 230 .

The communication unit 210 may include one or more components that allow the server 200 to communicate with another device (not shown) and a server (not shown). The other device (not shown) may be a computing device such as the server 200 or a sensing device, but is not limited thereto. The communication unit 210 may receive a user input from another electronic device or data stored in an external device from an external device through a network.

The DB 230 may store a program for processing and controlling the processor 220 . For example, the DB 230 may store an instruction for providing a service. Also, the DB 230 may store data generated by the processor 220 . For example, the DB 230 may store information related to an optical sensor calibration method provided by the processor 220 . The DB 230 may store information input to or output from the server 200 .

The processor 220 is ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), controllers (controllers), microcontroller It may be implemented using at least one of (micro-controllers), microprocessors, and other electrical units for performing functions.

The DB 230 may store at least one instruction executed through the processor 220 . The at least one instruction irradiates light to standard particles generated from the particle generator; detecting the number by size of particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light; determining a central channel based on the number of each size of the particles; And it may be set to calibrate the optical sensor so that the central channel has a preset channel value.

Here, the size of the particles may be classified into 254 channels.

Here, the central channel may be determined based on a first channel having the largest number of particles among candidate channels having a size difference between the preset channel and a preset first threshold value.

Here, the at least one command includes: calculating a difference value between the preset channel and the center channel; And it may be further set to move the particle size detected by the optical sensor by the difference value.

Here, the preset channel may be determined based on the size of the standard particle.

3 is a diagram illustrating an embodiment of a method of operating a particle meter in the air.

Referring to FIG. 3 , the air particle meter may irradiate light to standard particles ( S300 ). For example, an airborne particle meter may irradiate light to standard particles generated from a particle generator.

The air particle meter may detect the number of particles by size (S310). For example, the particle meter in the air may detect the number of each size of the particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light.

The particle generator can generate particles of a specific size (eg, 3 um). However, even if the particle generator is set to generate particles of 3 micrometers, the particle generator does not only generate particles of 3 micrometers, but may generate particles larger or smaller than 3 micrometers.

Airborne particle detectors can illuminate particles generated from a particle generator. When light is irradiated to the particles, the light irradiated to the particles may be scattered. The air particle meter can measure the amount of scattered light of the light scattered from the particles. As the size of the particles increases, the amount of scattered light may increase. Accordingly, as the size of the particles increases, the voltage level according to the amount of scattered light may increase. Therefore, the air particle meter can measure the size of the particles based on the amount of scattered light. The air particle meter can measure the size of each particle and record the number of particles for each size.

For example, the size of the particles may be classified into 254 channels. For example, among the particles to be measured, the smallest particle may be classified into 1 channel, and the largest particle may be classified into 254 channels.

4 is a diagram illustrating an embodiment in which an optical sensor detects particles.

Referring to FIG. 4 , the optical sensor (ie, a particle measuring device in the air) may irradiate light to the particles, and measure the amount of scattered light to measure the size of the particles. The optical sensor may measure the size of each particle to obtain information on the number of particles for each size.

5 is a view showing measurement results of optical sensors measuring the same standard particle.

Referring to FIG. 5 , even when the same standard particle is measured, an error may occur for each optical sensor. For example, sensor 1, sensor 2, sensor 3, and sensor 4 can all measure standard particles of 3 μm. The standard particles measured by sensors 1 to 4 are all standard particles of the same size, but the voltage level of the particles measured by each sensor may be different. That is, a measurement error may occur in each of the sensors.

Therefore, it is necessary to correct the errors of the optical sensors.

6 is a diagram illustrating an example of a calibration result using a channel mass value.

Referring to FIG. 6 , the sensor may be calibrated based on channel mass values of particles measured by the sensor. For example, the mass of the particles in each channel of the different sensors can be calibrated with a mass factor to have a similar pattern. However, it is difficult to make a perfect correction using such a channel mass value.

Existing dust meters perform calibration only with a mass factor. When only the mass factor is calibrated at a specific location, if the particle composition (for example, the number of particles for various sizes ranging from large particles to small particles) in a specific location changes, the standard particle intrinsic voltage value of each sensor is not calibrated. Sensor deviation occurs again.

Therefore, a new calibration method for matching the particle measurement size channel proposed in the present specification is described below.

Referring back to FIG. 3 , the air particle meter may determine the center channel ( S320 ). For example, the air particle meter may determine the central channel based on the number of each size of the particles.

The center channel is a concept defined for calibration of optical sensors in this specification, and by matching the center channel of each sensor, it is possible to effectively calibrate each sensor.

The center channel is a channel determined based on the distribution tendency of particles when the sensor measures standard particles, and sensors can be calibrated by moving the center channel of the sensors to match the theoretically calculated center channel.

For example, the central channel may be determined based on a first channel having the largest number of particles among candidate channels having a difference in size between a preset channel and a preset first threshold.

For example, the preset channel may be determined based on the size of the standard particle.

7 is a diagram illustrating an embodiment of a center channel.

Referring to FIG. 7 , channel 43 may be a central channel. When standard particles are measured, a lot of small particles are generated as shown in FIG. 7 , and thus, the number of particles in channels having a small particle size tends to be measured very high. When measuring the central channel, small particles can be ignored and channels near the standard particle size can be observed. For example, when a standard particle of 3 μm is generated, a central channel can be found in the vicinity of a channel corresponding to 3 μm.

When the sensors measure the standard particle size, the particle number distribution according to the particle size tends to increase and then decrease again in the vicinity of the standard particle size channel after noise caused by small particles. The highest point of the peak that occurs as the number of particles increases according to the particle size and decreases according to the particle size can be defined as the central channel. That is, in FIG. 7 , channel 43 may be a central channel.

Referring back to FIG. 3 , the air particle detector may calibrate the optical sensor ( S330 ). For example, an airborne particle detector may calibrate the optical sensor so that the central channel has a preset channel value.

For example, the air particle detector may calculate a difference value between the preset channel and the central channel, and may move the particle size detected by the optical sensor by the difference value.

That is, the preset channel may be the theoretically calculated value of the central channel. Thus, if the optical sensor measures a standard particle, it can find the optical sensor's central channel, and by calibrating the optical sensor's central channel to match the theoretical central channel, the optical sensor can be calibrated.

The step of determining the center channel based on the standard particle measurement result of the optical sensor may include a series of steps as follows.

1. A step of specifying a first channel having the largest number of particles from among candidate channels having a difference in size within a preset first threshold value from a preset channel.

For example, if the preset channel (ie, the theoretical center channel value) is channel 43, candidate channels (ie, channel) with a difference in magnitude within the preset first threshold value (eg, 20 channels) A channel having the largest number of particles among channels 23 through 63 may be specified as a first channel (eg, channel 26).

2. Checking whether the number of particles in the first channel is the largest among the first verification channels having a difference between the first channel and a size within a second preset threshold.

For example, a first verify channel (eg, channel 16 through channel 36) that differs in magnitude within a first channel (eg, channel 26) and a second threshold (eg, 10 channels) Among them, the number of particles in the first channel may be smaller than the number of particles in other channels (eg, channel 16) included in the first verification channel. Here, when the number of particles of the first channel is the largest among the number of particles of other channels included in the first verification channel, the first channel becomes the central channel.

3. Based on the fact that the number of particles in the first channel is not the largest among the first verification channels having a difference in size within the second threshold value from the first channel, the number of particles among the candidate channels is 2 determining the second largest number of channels.

For example, since the number of particles in the first channel (eg, channel 16) is the highest among the first verification channels (eg, channel 16 through channel 36), candidate channels (eg, channel 23 through channel 63) ), a second channel (eg, channel 36) having the second largest number of particles may be determined.

4. Checking whether the number of particles in the second channel is the largest among the second verification channels having a difference between the second channel and the second channel in size within the second threshold.

For example, the second channel (eg, channel 36) and the second verification channel (eg, channel 26 to channel 46) differing in magnitude within a second threshold (eg, 10 channels) ), the number of the second channels (eg, channel 36) may be the largest.

5. Determining the second channel as the central channel based on the second channel having the largest number of particles among second verification channels having a difference in size within the second threshold value from the second channel .

For example, since the number of second channels (eg, channel 36) has the largest number of particles among the second verification channels, the second channel (eg, channel 36) may be determined as the central channel.

Thereafter, the airborne particle detector can calibrate the optical sensor so that the central channel (ie, channel 36) has a preset channel value (ie, channel 43).

For example, the airborne particle detector may calculate a difference value (ie, 7 channels) between the preset channel and the central channel, and determine the particle size detected by the optical sensor as the difference value (ie 7 channels). ) can be moved.

That is, the measurement result of the number of particles for each particle size of the air particle meter may be switched to the right by 7 channel values. In other words, the particle size of the airborne particle meter can be calibrated as large as all 7 channels. For example, if the particle size of an airborne particle meter is measured with channel 36, it may actually be considered to be the particle size of channel 43.

8 is a diagram illustrating an embodiment of the result of not performing center channel calibration with the equipment performing center channel calibration, and FIG. 9 is a diagram illustrating an example of the result of performing center channel calibration.

Referring to FIGS. 8 and 9 , it can be seen that the calibration results using the center channel have been corrected to have very similar results when measuring fine dust of each sensor. That is, it can be seen that the optical sensors subjected to the center channel calibration method of the present specification were calibrated to obtain almost similar results when exposed to the same environment.

Some of the detailed steps shown in the example of FIG. 3 may not be essential steps and may be omitted. In addition to the steps shown in FIG. 3 , other steps may be added, and the order of the steps may vary. Some of the above steps may have their own technical meaning.

A calibration method of an optical sensor performed in at least one airborne particle measuring device, the method comprising: irradiating light to standard particles generated from a particle generator; detecting the number by size of particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light; determining a center channel based on the number of each size of the particles; and calibrating the optical sensor so that the central channel has a preset channel value.

Here, the size of the particles may be classified into 254 channels.

Here, the central channel may be determined based on a first channel having the largest number of particles among candidate channels having a size difference between the preset channel and a preset first threshold value.

Here, calibrating the optical sensor so that the central channel has a preset channel value may include: calculating a difference value between the preset channel and the central channel; and moving the particle size detected by the optical sensor by the difference value.

Here, the preset channel may be determined based on the size of the standard particle.

Here, the determining of the central channel includes checking whether the number of particles in the first channel is the largest among the first verification channels having a difference in size within a second threshold value set in advance from the first channel. step; Based on the fact that the number of particles in the first channel is not the most among the first verification channels having a difference in size within a second threshold value from the first channel, the number of particles is second among the candidate channels. determining a number of second channels; checking whether the second channel has the largest number of particles among second verification channels having a difference between the second channel and the second channel in size within the second threshold; and determining the second channel as the central channel based on the second channel having the largest number of particles among the second verification channels having a difference in size within the second threshold value from the second channel. may include

The operation according to the embodiment of the present specification may be implemented as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored. In addition, the computer-readable recording medium may be distributed in a network-connected computer system to store and execute computer-readable programs or codes in a distributed manner.

When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) that performs the above-described function. A module may be stored in a memory and executed by a processor. The memory may be internal or external to the processor, and may be coupled to the processor by various well-known means.

In addition, the computer-readable recording medium may include a hardware device specially configured to store and execute program instructions, such as ROM, RAM, and flash memory. The program instructions may include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

Although some aspects of the invention have been described in the context of an apparatus, it may also represent a description according to a corresponding method, wherein a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method may also represent a corresponding block or item or a corresponding device feature. Some or all of the method steps may be performed by (or using) a hardware device such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps may be performed by such an apparatus.

In embodiments, a programmable logic device (eg, a field programmable gate array) may be used to perform some or all of the functions of the methods described herein. In embodiments, the field programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

The various embodiments described above may be embodied in other specific forms without departing from the technical idea and essential characteristics thereof. Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the various embodiments should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the various embodiments are included in the scope of the various embodiments. In addition, claims that are not explicitly cited in the claims can be combined to form an embodiment or included as a new claim by amendment after filing.

Claims (5)

In the calibration method of the optical sensor (light scattering sensor) carried out in at least one airborne particle meter,
Irradiating light to standard particles generated from a particle generator;
Detecting the number by size of particles included in the standard particles based on the number of light scattered by the standard particles and the amount of scattered light, the size of the particles being classified into 50 or more channels;
determining a first channel having the largest number of particles from among candidate channels having a difference between a preset channel and a preset first threshold in size;
checking whether the number of particles of the first channel is the largest among first verification channels having a difference between the first channel and a size within a preset second threshold;
Based on the fact that the number of particles in the first channel is not the most among the first verification channels having a difference in size within a second threshold value from the first channel, the number of particles is second among the candidate channels. determining a number of second channels;
checking whether the second channel has the largest number of particles among second verification channels having a difference between the second channel and the second channel in size within the second threshold;
determining the second channel as a central channel based on the second channel having the largest number of particles among second verification channels having a difference in size within the second threshold value; and
calibrating the optical sensor such that the central channel has the preset channel value;
How to calibrate an optical sensor.
delete delete The method according to claim 1,
calibrating the optical sensor so that the central channel has a preset channel value,
calculating a difference value between the preset channel and the center channel; and
moving the particle size detected by the optical sensor by the difference value,
How to calibrate an optical sensor.
5. The method of claim 4,
The preset channel is determined based on the size of the standard particle,
How to calibrate an optical sensor.

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